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Researchers have developed and characterized a room-temperature RF Board that converts frequency signals for reading data from quantum detectors called transition-edge sensors (TES). The board successfully converts baseband signals (0-4 GHz) to radio frequency signals (4-8 GHz) and back again, achieving the required power levels of -31.06 to -25.53 dBm for outgoing signals and an estimated -45 to -35 dBm for returned signals. Testing confirms the RF Board meets all specifications for the microwave SQUID multiplexing readout system used in the AliCPT experiment, which can handle 1000 tones simultaneously.
Why it matters
This technology enables the readout of large arrays of highly sensitive quantum detectors used in cosmology experiments and other precision measurement applications. The successful development of this electronics system is crucial for scaling up detector arrays to thousands of sensors, which is necessary for next-generation astronomical observations and fundamental physics research.
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⚠️ Preprint – Noch nicht peer-reviewed
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Abstract: Microwave SQUID multiplexing ($mu$MUX) is a widely used readout technique for large-scale transition-edge sensor (TES) arrays. It uses radio-frequency (RF) probe tones to interrogate cryogenic resonators, requiring frequency conversion between the baseband electronics and the cryogenic RF signal chain. This work describes the RF Board, a room-temperature frequency-conversion board deployed in the AliCPT $mu$MUX readout system. The board up-converts 0-4 GHz baseband I/Q signals to the 4-8 GHz RF band for injection into the cryogenic chain and down-converts returned RF signals to baseband I/Q for ADC digitization. For the current 1000-tone operation, with a DAC output tone power of -30 dBm/tone, the required power windows are -35 to -25 dBm/tone for the RF tones transmitted to the cryostat and -45 to -35 dBm/tone at the ADC input for the returned tones. The RF Board is characterized using swept single-tone measurements covering up-conversion, down-conversion, and RF loopback. Based on these measurements, the RF output power is calculated to be -31.06 to -25.53 dBm, satisfying the RF output window. Assuming a representative cryogenic-chain transmission of -40 dB, the loopback result gives an estimated returned power of -45 to -35 dBm, within the target range. These results show that the RF Board meets the wideband frequency-conversion and tone-power requirements for the $mu$MUX readout system.
Source: Characterization of the RF Board for microwave SQUID multiplexing readout electronics